Externals: Add glslang from Vulkan SDK v1.0.21.1

Externals/glslang/gtests/Initializer.h

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+//
+// Copyright (C) 2016 Google, Inc.
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+//
+//    Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+//
+//    Redistributions in binary form must reproduce the above
+//    copyright notice, this list of conditions and the following
+//    disclaimer in the documentation and/or other materials provided
+//    with the distribution.
+//
+//    Neither the name of Google Inc. nor the names of its
+//    contributors may be used to endorse or promote products derived
+//    from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+// COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GLSLANG_GTESTS_INITIALIZER_H
+#define GLSLANG_GTESTS_INITIALIZER_H
+
+#include "glslang/Public/ShaderLang.h"
+
+namespace glslangtest {
+
+// Initializes glslang on creation, and destroys it on completion.
+// And provides .Acquire() as a way to reinitialize glslang if semantics change.
+// This object is expected to be a singleton, so that internal glslang state
+// can be correctly handled.
+//
+// TODO(antiagainst): It's a known bug that some of the internal states need to
+// be reset if semantics change:
+//   https://github.com/KhronosGroup/glslang/issues/166
+// Therefore, the following mechanism is needed. Remove this once the above bug
+// gets fixed.
+class GlslangInitializer {
+public:
+    GlslangInitializer() : lastMessages(EShMsgCascadingErrors)
+    {
+        glslang::InitializeProcess();
+    }
+
+    ~GlslangInitializer() { glslang::FinalizeProcess(); }
+
+    // A token indicates that the glslang is reinitialized (if necessary) to the
+    // required semantics. And that won't change until the token is destroyed.
+    class InitializationToken {
+    };
+
+    // Re-initializes glsl state iff the previous messages and the current
+    // messages are incompatible.  We assume external synchronization, i.e.
+    // there is at most one acquired token at any one time.
+    InitializationToken acquire(EShMessages new_messages)
+    {
+        if ((lastMessages ^ new_messages) &
+            (EShMsgVulkanRules | EShMsgSpvRules | EShMsgReadHlsl)) {
+            glslang::FinalizeProcess();
+            glslang::InitializeProcess();
+        }
+        lastMessages = new_messages;
+        return InitializationToken();
+    }
+
+private:
+
+    EShMessages lastMessages;
+};
+
+}  // namespace glslangtest
+
+#endif  // GLSLANG_GTESTS_INITIALIZER_H